Three charges +q, -q and +q are kept at the corners of an equilateral triangle of side d. Find the resultant electric force on a charge +q placed at the centroid O of the triangle.

Explanation

To solve the problem of finding the resultant electric force on a charge \( +q \) placed at the centroid \( O \) of an equilateral triangle with charges \( +q \), \( -q \), and \( +q \) at its vertices, follow these steps:

### Step-by-Step Solution:

1. **Identify the Geometry and Charges:**
- Consider an equilateral triangle with vertices \( A \), \( B \), and \( C \).
- Place charges \( +q \) at \( A \), \( -q \) at \( B \), and \( +q \) at \( C \).
- Place a charge \( +q \) at the centroid \( O \).
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